Vintage Double Hose

I have rebuilt my DA now and am getting around 0.8 inches cracking pressure on my mangahelic. I have connected a multi-port adapter to the hookah port and connected my bcd and octopus. (Looks like a Christmas tree). However the breathing resistance seems high on the octopus. Certainly higher than when it is connected to a single hose first stage and the inflation rate on my bcd seems a little slower. Is this normal? The octopus and bcd are quite useable though.

It sounds like your intermediate pressure (IP) of your DA is set lower than your single hose first stage is set. You may be able to increase the IP a little on your DA. If that is not successful or causes air seep you can try adjusting the Octopus. You might even want to try that first if you have the DA breathing the way you like and had rather not readjust it.

If the octopus has an adjustable orifice you can back it out a little to decrease the spring tension, thereby lowering the cracking effort. That will probably require a readjustment of the lever height to prevent a free flow, but the higher you can get the lever without leaking air the easier it will breathe.

Do you have a way to check your IP on both regs? Compare that before starting and we will have a little more info to go on for further suggestions.

Good luck.

I agree and keep in mind the DA is an unbalanced diaphragm so it's IP will shift and will be lower at high tank pressures.

An inexpensive IP gauge hooked to your bc hose will go a long way to diagnosing what's really going on.

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What is the IP set at and how was it done. The ideal way is at a tank pressure of 200 to 300 psi and set at 130 to 140 psi. IP will decrease to about 110 psi on a full tank (2500 psi). Most balanced single hoses have an IP in the 130 to 140+ range so you can expect some reduction in octo performance with a full tank considering the lower IP and increase in flow resistance in the hose and multi port adapter.

All of the above is spot on advice.

I would like to add to the above by saying that this is a perfect place to have an adjustable, or a balanced second stage; or the best of both worlds: a balanced/adjustable second stage octopus as both of those features help to compensate for the unbalanced first stage.

I checked the IP on the DA and it was 118 at 2200 psi. I did not check the IP on the single hose yet, but from memory it runs around 140, 150 psi, so that explains the reason why it breathes so badly. Thanks.

Have you breathed from the Octo while underwater or just on the bench?
Sometimes they don't seem so bad underwater compared to during set up when I am so particular about performance.

Taking it into the pool and down to about 4 meters is in my plan for next weekend. Right now it is set up and sitting in the basement in all its glory. It has the pressure gauge on a banjo and a 3 port swivel for the BCD and octo, plus a 20 cu ft pony on a STA on the cam band. Hardly minimalistic vintage. I am pretty confident I don't need the pony, but since this is my first rebuild and I had the bottle anyway, I thought I would feel pretty silly drowning because I had left it in the garage at home. This will come along for the pool test, because it is how I intend to dive it for the first couple of runs and I want to see what the pony does to my trim.